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Full text of "Modern Mechanical Engineering Vol-I"

66

PATTERN-MAKING

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of buckets. The supplementary open spaces are equivalent to the extra
length allowed on cores to enter print impressions. But in this case the
cores are simply set to lines described on a levelled bed of sand, and,
mutually abutting by their supplementary portions, they complete the ring.
Plain, rectangular boxes are rammed on a core bench. A bottom board
is necessary when bosses and other fittings have to be located correctly.
The sides fit this with dowels or with strips on the board. Often one or

Fig. 24.óCore Box with Strickle for Curved Portions

two faces of a core are curved. Then, when practicable, strickling is resorted
to (fig. 24), as it is also for the upper plane faces of cores. This economy in
curved portions is that due to the saving of timber and of the time occupied
in shaping it to the curves.

CHAPTER  II
Examples of Work
Pattern-making includes many departments. The work done on patterns
for a brass foundry is wholly different from that done on patterns for the
heavier castings of the marine engine, the locomotive, and the larger types of
pumps, while the making of core boxes for gas and automobile cylinders calls
for special ingenuity and skill. The construction of patterns for cranes,
gear wheels, pipes, and columns, each enlists the services of men who have
developed into specialists. In every large shop certain groups of patterns
go to men who seldom handle anything else. But a trained, intelligent man
is, or should be, able to take up any branch of his trade when required to do
so. The principles that underlie the practice are unchangeable. It is from
this chiefly, the general standpoint, that the subject will be regarded in this
section.